OP, one thing you didn't mention was what size (if any) hills did you climb and if the wind direction was in your favor during this 50 miler?
I just got back from a 35 mile ride, which I completed in 2 hours and 45 minutes, mostly flat but with headwind the whole way. I would have been faster but the last five miles or so I ran out of water (the one time I decided to go on a long ride without my camelback!) and it was 95 degrees so I think I was starting to get dehydrated towards the "finish line". I like setting goals for myself, whether its related to weight loss, biking, or life in general. I started out with one biking goal, being a 50 mile finale to complete by the end of the summer - Now it seems like just completing 50 miles isn't enough, but I would like to complete it within three hours.